linux-kernel - Re: [PATCH 1/7] drm: atmel-hlcdc: add config option for clock selection

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Message-ID: <21942343-5e76-2fa3-b394-c1cef4abd9e1@microchip.com>
Date:   Fri, 1 Mar 2019 10:07:02 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <sam@...nborg.org>
CC:     <lee.jones@...aro.org>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>,
        <bbrezillon@...nel.org>, <airlied@...ux.ie>, <daniel@...ll.ch>,
        <thierry.reding@...il.com>, <devicetree@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/7] drm: atmel-hlcdc: add config option for clock
 selection



On 28.02.2019 23:25, Sam Ravnborg wrote:
> Hi Claudiu
> 
> On Wed, Feb 27, 2019 at 04:24:16PM +0000, Claudiu.Beznea@...rochip.com wrote:
>> From: Claudiu Beznea <claudiu.beznea@...rochip.com>
>>
>> SAM9x60 LCD Controller has no option to select clock source as previous
>> controllers have. To be able to use the same driver even for this LCD
>> controller add a config option to know if controller supports this.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
>> ---
>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 12 +++++++-----
>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.h   |  2 ++
>>  2 files changed, 9 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
>> index 8070a558d7b1..17a7a18f6a07 100644
>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
>> @@ -78,7 +78,8 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
>>  	unsigned long mode_rate;
>>  	struct videomode vm;
>>  	unsigned long prate;
>> -	unsigned int cfg;
>> +	unsigned int mask = ATMEL_HLCDC_CLKDIV_MASK | ATMEL_HLCDC_CLKPOL;
>> +	unsigned int cfg = 0;
>>  	int div;
> Here cfg and mask has initial values.
> 
>>  
>>  	vm.vfront_porch = adj->crtc_vsync_start - adj->crtc_vdisplay;
>> @@ -101,7 +102,10 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
>>  		     (adj->crtc_hdisplay - 1) |
>>  		     ((adj->crtc_vdisplay - 1) << 16));
>>  
>> -	cfg = ATMEL_HLCDC_CLKSEL;
>> +	if (!crtc->dc->desc->fixed_clksrc) {
>> +		cfg = ATMEL_HLCDC_CLKSEL;
>> +		mask |= ATMEL_HLCDC_CLKSEL;
>> +	}
> And here mask is bitwise or with ATMEL_HLCDC_CLKSEL - fine.
> But cfg is directly assigned.

I directly assigned it here because it was the first time it was used.
I will use a "|" operation as you suggest in next version.

> If cfg was bitwise or the ATMEL_HLCDC_CLKSEL value then the code was prepared
> to have extra flags added above these lines.
> 
> Only a small change and no functional difference.
> 
> With or without this change:
> Reviewed-by: Sam Ravnborg <sam@...nborg.org>
> 
>